FR to US conversion

FR 100D in US Bra Size

Convert 100D from French sizing to US sizing, with the full international table, sister sizes, and practical fit checks in one place.

Instant answer

100D (FR) =

38D US

In this sizing table, 100D in French sizing converts to 38D in US sizing.

Full conversion table for 100D (US 38D)

38D bra size conversion across US, UK, EU, French, and Australian sizing.
US	UK	EU	FR	AU
38D	38D	85D	100D	16D

Bra sizing varies between brands. Use this as an accurate starting point and check the fit.

What this conversion means

100D is the French label in this dataset, and it points back to 38D in US sizing. The band number may change a lot between systems, especially for EU and French labels, but the table keeps the intended fit target together.

Sister sizes for the US equivalent (38D)

Sister sizes: 36DD and 40C can be worth checking when the cup volume feels close but the band needs a different feel.

What measurements make a 100D?

100D is built from a band measurement and a bust measurement, not from the label alone. In the current calculator formula, the closest starting range is about 37-39 inches (94-99 cm) under the bust and about 41.5-42.5 inches (105-108 cm) around the fullest part of the bust. The band comes from the underbust rounding, while the cup step comes from the difference between bust and band. This page uses 38D as the US equivalent for those measurement notes.

Is 100D big or small?

100D is not automatically big or small; it depends on the band and the cup together. In this size set, the US equivalent uses a fuller band and a middle cup step. Cup letters are relative to the band, so a D on one band is not the same volume as a D on every other band. The most useful question is whether the band stays level and the cups hold smoothly, not whether the label sounds large or small.

If 100D doesn't fit right

Band rides up: The band may be too loose or stretched out; try a snugger band or compare the snugger sister size.

Cups gape: The cup may be too roomy, too deep, or pulled away by a loose band; check the band before changing cup volume.

Cups spill: The cup volume may be too small or the cup shape may be too closed; try one cup step up before changing the band.

Straps dig in: The straps may be compensating for a band that is not supporting enough; reset the band fit before tightening straps.

How 100D differs between brands

Two brands can print 100D or its equivalent on the tag and still cut the bra differently. A firmer elastic can make the same band feel smaller, and a shallow or narrow cup can make the same cup letter feel different. Check the retailer chart, read fit notes when available, and compare the label against the brand and region sizing guide before treating the conversion as final.

Shopping for 100D

When shopping for 100D, start with styles that make the band easy to judge. If the cup is in a lower or middle step, lightly lined T-shirt styles can make gaps easy to spot. Fuller cup steps often benefit from styles with steadier side support, deeper cups, or a balconette shape depending on breast shape. For special outfits, compare the fit needs in the outfit guides before choosing a strapless, plunge, or backless option.

Bras in your size

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Everyday Fit Store

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Comfort Band Co.

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Soft Cup Edit

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FAQ

Is 100D the same as 38D in the US?

In this dataset, 100D (FR) converts to 38D in US sizing. Some brands publish their own charts, so use this as the closest standard label and still check the real fit.

What is 100D in Australian sizing?

100D (FR) matches the same base record as 16D (AU). The full table on this page shows each supported label side by side.

How do I check the fit of 38D?

Start with the band: it should feel firm and even around your ribcage. Then check cup containment, wire comfort, and whether the center gore lies close on wired styles.

What sister sizes work with 38D?

36DD and 40C are the closest sister-size options for 38D in this dataset. Try a sister size when cup volume feels close but the band needs to feel snugger or looser.

Why do bra sizes differ between countries?

Bra labels are written differently across US, UK, EU, French, and Australian systems. Cup letters can also diverge after D, so a converted label is a starting point rather than a promise of identical fit.

What measurements usually make 100D?

100D maps to US 38D here. The current calculator formula points to about 37-39 inches underbust and 41.5-42.5 inches bust, or roughly 94-99 cm and 105-108 cm. Treat that as a starting range and then check the real fit.